Susten 100 mg Injection 1 ml is used in the treatment of dysfunctional uterine bleeding threatened abortion, and amenorrhoea. It is also used in the maintenance of early pregnancy. This medicine contains progesterone, a female hormone which helps increase the progesterone levels in the body. Common side effects include injection site reactions, rash or any other allergy, changes in the breast, darkening of facial skin, scalp hair loss, coarsening of hair in abnormal regions.